Debt Securities Available for Sale - AFS debt securities in a continuous unrealized loss position (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 4,893,224	$ 287,277
Less than 12 months Gross Unrealized Losses	4,143	5,566
12 months or more Fair Value	11,455,977	12,455,131
12 months or more Gross Unrealized Losses	1,441,639	1,367,947
Total Fair Value	16,349,201	12,742,408
Total Gross Unrealized Losses	1,445,782	1,373,513
US Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	4,845,109	244,925
Less than 12 months Gross Unrealized Losses	3,713	5,126
12 months or more Fair Value	5,809,606	6,550,941
12 months or more Gross Unrealized Losses	234,370	257,662
Total Fair Value	10,654,715	6,795,866
Total Gross Unrealized Losses	238,083	262,788
Collateralized Mortgage Obligations - Federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	2,127	5,234
Less than 12 months Gross Unrealized Losses	2	35
12 months or more Fair Value	123,238	124,930
12 months or more Gross Unrealized Losses	12,154	11,992
Total Fair Value	125,365	130,164
Total Gross Unrealized Losses	12,156	12,027
Mortgage Backed Securities - federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	45,988	37,118
Less than 12 months Gross Unrealized Losses	428	405
12 months or more Fair Value	5,523,133	5,779,260
12 months or more Gross Unrealized Losses	1,195,115	1,098,293
Total Fair Value	5,569,121	5,816,378
Total Gross Unrealized Losses	$ 1,195,543	$ 1,098,698